Experimental Technique

Combining the low divergence of the 4th light source, twin EPUs, chopper modulation and lock-in amplification, high-sensitivity XMCD measurements are achieved. Using ultra-small beam spot down to 3 micrometers with KB mirrors and ferromagnetic resonance technology, XFMR measurements with a phase time resolution of 5 ps are realized. Utilizing a dual-layer cooling system (liquid nitrogen coil shield + thermo-insulation shield + liquid helium), PEEM measurements are performed in a liquid helium temperature (20 K) with a spatial resolution of ~20 nm.

Beamline optics

Superconducting Magnet Endstation

Overview

The beamline is sourced by twin elliptically polarizing undulators (EPU43.5). The twin EPUs can operates in parallel and collinear modes. A plane mirror M1 deflects the beam by 2° to reduce the heat load and cut off the high energy X-rays. The monochromator is a variable-line-spacing plane grating monochromator type, consisting a plane mirror and two different gratings. Monochromatized X-ray beam is switchable into two branches by the ellipsoidal cylindrical mirror M3. The parallel beams is reflected to the exist slit by M3. Then they are reflected by M6 and further focused by KB mirror set (M7&8) to the Superconducting Magnet (SCM) Endstation and Cryo-PEEM Endstation. A chopper is place behind the exist slit to make the parallel beams alternately illuminating the SCM Endstation. The beam sizes at the SCM Endstation and PEEM Endstation are 200×40 m and 26×53 m. When M3 removed from optical path, the collinear beams are reflected and focused by KB mirror set (M4&5) to the Vector Magnet (VM) Endstation. The beam sizes at the VM Endstation is  3×3 m.

Key Performance

Experimental End-station

A-Branch: SCM-XMCD

Key Performance

Overview

Branch A is a SCM-XMCD end-station with the X-ray beam energy ranging from 250 eV to 2000 eV. Equipped with a superconducting magnetic filed of (9T or 2T, along or perpendicular to the incoming x-ray beam ), this end-station is designed to measure untra-weak magnetism of quantum materials.  

I. Load-lock 

  Up to 3 sample holders can be loaded (up to 4 samples/holder )

II. Main chamber

   X-rays with variable polarization (LH(0), LV(90), CR,CL)

   Beam polarization switch with high speed choppers (up to 1 KHz)

   In-situ multi-field environment (electric filed, stress)

   Different signal detection mode:  TEY， FY， Transmission

A-Branch: Cryo-PEEM

Key Performance

Overview

Cryo-PEEM endstation at BL04 beamline is characterized with a LHe manipulator offering a low temperature of 20 K for the sample imaging. A SR200 energy analyzer is equipped to gain an energy resolution less than 0.1 eV at the spectroscopic real space imaging mode. This endstation is dedicated to spatially resolve the chemical, electronic, and magnetic properties of novel magnetic and quantum materials with high resolution and elemental specificity. 

I. Loadlock 

  Up to 4 sample holders can be loaded to the parking chamber.

II. Preparation chamber

  Sample can be prepared or treated with sputtering and annealing up to 1200 K as well as cleaved in vacuum;

  Sputter gun; RHEED; 2 ports available for evaporators;  gas doser as required;    

III. Analysis chamber

　2 ports for evaporator installation; 

    LHe manipulator

    e-gun and mercury light source

    LEEM/PEEM/SPEPEEM/MEM/ARPES imaging modes

B-Branch: Vector Magnet Endstation

Key performance

Overview

Branch B is a vector magnet endstation, equipped with a vectorial magnetic field up to 0.9 T, a loadlock, a X-ray ferromagnetic resonance (XFMR) manipulator and XAS/XMCD/XMLD manipulator. This vector magnet endstation is designed to measure small-size spintronic device with probing spot size of 3μm ×3μm, ultrafast GHz magnetic dynamic process and spin current/orbital current transmission.

Ⅰ. Loadlock

Up to 6 samples can be loaded  (flag-type sample plate)

Ⅱ. XFMR manipulator

Frequency range: 0.5GHz-8GHz (Integer multiple of 0.5GHz)

Field of view: 500μm aperture, LY mode and FY mode, transverse FMR, sensitive to phase of precession

Ⅲ. XAS/XMCD/XMLD manipulator

Sample positions: 2 TEY and 1 LY

Science

Scientific Scope 1：This capability enables the quantitative measurement of weak magnetic signals in spintronic materials, empowered by a system that integrates parallel twin EPUs, beamline choppers, and lock-in amplification to enhance detection sensitivity by ~100x. The core aim is to build a bridge between microscopic properties (orbital/spin magnetic moments and local atomic/electronic structure) and macroscopic magnetic behavior. These insights are critical for laying the physical groundwork for intelligent material design.

Scientific Scope 2：Leveraging the 3-μm micro-focus capability of KB mirrors and the 5-ps phase-temporal resolution of XFMR, this platform enables temporal- and spatial-resolved  investigations of spin currents and spin waves in spin-orbit torque (SOT) and other prototype devices. These advances provide a critical tool for probing underlying mechanisms, such as spin current propagation (via coherent or thermal magnons) and the boundary conditions governing spin wave quantum effects.

Scientific Scope 3：The capability sample environment at liquid-helium temperature via dual-cooling technology, coupled with 20-nm spatial resolution of PEEM, allows this endstation to conduct magnetic domain structure imaging and spectroscopic mapping on emerging materials including 2D magnetic topological materials, their heterostructures and altermagnets, thereby providing a foundation for understanding their novel magnetic properties.

People

Useful Link

Related beamlines:

XMCD beamlines:

https://www.nsrl.ustc.edu.cn/10957/list.htm

https://www.helmholtz-berlin.de/pubbin/igama_output?modus=einzel&sprache=en&gid=1969&typoid=76454

PEEM beamlines:

https://www.maxiv.lu.se/beamlines-accelerators/beamlines/maxpeem/

https://sites.google.com/lbl.gov/bl11-peem3-als/home